US2987566A

US2987566A - Thermopile for operation by pilot burners

Info

Publication number: US2987566A
Application number: US841279A
Authority: US
Inventors: William A Ray
Original assignee: General Controls Co
Current assignee: General Controls Co
Priority date: 1959-09-21
Filing date: 1959-09-21
Publication date: 1961-06-06
Anticipated expiration: 1978-06-06

Description

W. A. RAY

THERMOPILE FOR OPERATION BY PILOT BURNERS June 6, 1961 2 Sheets-Sheet 1 Filed Sept. 21, 1959 INVENTOR.

fir TOEA/EYS,

June 6, 1961 w. A. RAY

THERMOPILE FOR OPERATION BY PILOT BURNERS Filed Sept. 21, 1959 2 Sheets-Sheet 2 NVENTOR. MAL/0M .40 E4).

A 7' TOENEYS.

2,987,566 THERMOPILE FOR OPERATION BY PILOT BURNERS This invention relates to thermopile generators. Thermopiles are now in common use for supplying controlling current in connection with fuel burners. A typical installation is one in which a pilot burner serves as the source of heat, and the electrical energy generated by the thermopile serves to maintain a safety valve open. When the pilot burner is extinguished for any reason, the safety valve automatically closes, interrupting the flow of fuel to the main burner.

Such thermopiles are made up of a series of thermocouples, each forming a hot junction and a cold between dissimilar metals or alloys, such as Chromel and copal. The generation of electrical energy by providing a temperature differential between the hot and cold junctions is now a well-understood phenomenon.

In order to produce the desired operating potential difference across the terminals of the thermopile, it is common to employ as many as thirty or forty couples.

It is one of the objects of this invention to make it possible to arrange the couples in such a thermopile in a compact fashion, and in such manner that the temperature differential between the hot and cold junctions is maintained at a high value.

In furtherance of this object, the thermopile is so arranged that the hot junctions are substantially uniformly subjected to the pilot flame, and the cold junctions are also so disposed as to provide efiicient transfer of heat away from them.

It is, accordingly, another object of this invention to improve, in general, thermopile structures of this character.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of the invention. For this purpose, there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

FIGURE 1 is an enlarged longitudinal section of a thermopile structure shown as installed on a pilot burner;

FIG. 2 is a still further enlarged sectional view, taken along a plane corresponding to line 22 of FIG. 1;

FIG. 3 is an isometric view of the upper portion of the thermopile shown in FIG. 1, and in section;

FIG. 4 is an enlarged fragmentary sectional view, similar to FIG. 1, of a modified form of the invention;

FIG. 5 is a sectional view, taken along a plane corresponding to line 55 of FIG. 4; and

FIG. 6 is a diagram showing the connections between the inner and outer series of thermocouples forming the complete thermopile.

In FIG. 1, the thermopile structure 1 is shown as supported in any convenient manner in a bracket 2 forming a part of a pilot burner structure 3. The bracket 2 is provided with a recess 4 in communication with the supply of gas to the pilot burner. The gas proceeds through a series of jet openings formed by slots in a ring 5 disposed on a shoulder formed in the recess 4. The flame 6 serves to heat the upper end of the thermopile structure 1 for the generation of electrical energy.

2,987,566 Patented June 6, 1961 Such an arrangement is generally shown in prior Patent No. 2,677,004, issued April 27, 1954, in the name of Laurence C. Biggle.

The jacket 7 (FIGS. 1, 2 and 3), which encloses all of the active elements of the thermopile, may be in the form of thin metal having good heat-conducting properties, and generally of cylindrical form.

Located within this jacket 7 are two series of

thermocouples

8 and 13. Each series is rolled into annular form about the axis of the jacket. This is possible since the conductors or strips of the couple are relatively thin and flexible. The interior surface of the jacket 7 forms an envelope for the outer series 8.

The outer series 8 is diagrammatically illustrated in FIG. 6, and comprises alternate strips of dissimilar metals forming the thermopile. Thus, the longer strips 9 may alternate with the shorter strips 10, all of the strips 9 being formed of material differing thermoelectrically from the material of the shorter strips 8. For example, the longer strips may be made of copal, and the shorter strips of Chromel, or vice versa.

The outer annular series 8 may comprise any desired number of individual thermopiles. For example, there may be twenty-four in this outer series, the individual conductors being so arranged as to have their sides substantially radial of the annular structure. The outer series of thermocouples 8 is appropriately insulated from the jacket 7 as by the aid of the

mica insulation material

11 and 12. The hot junctions a are at the top, and the cold junctions b at the bottom.

The inner series of thermocouples 13 is illustrated diagrammatically in FIG. 6. This series of thermocouples is insulated from the outer series 8 by the aid of the hereinabove-described cylindrical insulation member 12, and is formed as an inner annulus.

This series of thermocouples 13 has alternate long and

short elements

14 and 15 joined together, as illustrated diagrammatically in FIG. 6. The hot junctions c are at the top, and the cold junctions d at the bottom. The two

series

8 and 13 are intended to be connected in appropriate series-assisting relationship by the aid of the lead 16 (FIGS. 1 and 6), and the

connections

17 and 18 to the ends of the completed thermocouple series correspond to the terminals of the thermopile.

The end thermocouple elements, as illustrated in FIG. 6, are properly made longer to provide

appropriate connection tabs

9a, 10a, 13a and 15a (FIG. 6).

A plug 19 of ceramic insulation material is disposed within the inner annular series 13 to hold the assembly properly in place, with the outer annular series 8 urged into contact with the insulation layer 11.

In the usual thermocouple structure with only a single annular series of thermocouples, the hot junctions a, as viewed in FIG. 1, would be substantially uniformly subjected to the heat of the flame 6. In order to ensure that the hot junctions c of the inner series 13 be under the full heating influence of the flame 6, these junctions are elevated beyond the junctions a of the outer annular series 8. For this purpose, the jacket 7 is extended beyond the hot junctions of the series 8. The extension 20 has the same external diameter as the main body of jacket 7. It is provided with a recess 21 of smaller diameter than the main body of the jacket 7 for the reception of the hot junctions c of the inner series 13. Appropriate

mica insulation layers

22 and 23 are provided to ensure against contact between the thermocouple elements and the extension 20.

Due to this construction, the flame 6 is substantially equally eifective for heating all of the hot junctions of the thermocouples.

The lower or cold junctions d of the inner series 13 extend substantially below those of the outer series 8.

Accordingly, due to this arrangement, transfer of heat away from the cold junction is not hindered by the outer annular series 8.

A plug of insulation material 24, such as a ceramic member, is placed in the lower end of the structure so as-to maintain the series of thermocouples in-proper relationship.

The jacket 7 extends downwardly into a tubular. supporting member 25. A brazing ring 26 serves to hold the twopar-ts. together. The end of the tubular member 25 provides a tubular extension 27 through which the insulated leads 28 and 29 extend.

Thel'eads or

terminals

17 and 18 are appropriately soldered

tothe conductors

28 and 29. These conductors are held in spaced-apart relationship by the aid of a spacer wall 31, and are appropriately supported at the lower end of the jacket.

Inthe form shown in FIGS. 4 and 5, the jacket 32 is provided with a hollow extension 33 of smaller diameter. Intothis smaller diameter extend the hot junctions of the inner series of thermocouples 34. In this instance, thethickness of the wall of jacket 32 is maintained substantially uniform. The thermopile operates inthe same manner as that disclosed in FIG. 1.

FIG. shows the outer annular series 35 appropriately insulated, as before, from the. jacket 32 and the inner annular series 34. This is accomplished by the aid of

mica elements

36, 37.

The structure of the thermopile at the lower end may be identical with that described in connection with the form shown-in FIG. 1.

Theinventor claims:

1. In a thermopile structure: a first series of thermocouples connected together and arranged annularly; a second series of thermocouples connected together and arranged annularly with the first series; the two series being connected in additive relation; the hot junctions of the second series being extended beyond the hot junctions of the first series; and a jacket enclosing the thermocouples and made from heat transmitting material.

2. In a thermopile structure: a first series of thermocouples connected together and arranged annularly; a

4, second series of thermocouples connected together and arranged annularly with the first series; the two series being connected in additive relation; the hot junctions of the second series being extended beyond the hot junctions of the first series; the cold junctions of the second series extending beyond the cold junctions of the first series; and a jacket enclosing the thermocouples and made from heat transmitting material.

3. In a thermopile structure: a first series of thermocouples conneoted together and arranged annularly; a second series of thermocouples connected together and arranged annularly with the first series; the two series being connected in additive relation; the hot junctions of the second seriesbeing extended beyond the hot junctions of the first series; and a jacket enclosing the thermocouples and made from heat transmitting material; said jacket having a stepped portion to conform to the projecting hot junctions of the second series.

4. In a thermopile structure: afirst series of thermocouples connected together and arranged annularly; a second series of thermocouples connected together and arranged annularly with the first series; the two series being connected in additive relation; the hot junetions of v the second series being extended beyond the hot junctions of the first series; the cold junctions. of the second series extending beyond the. cold junctions of the first series; and a jacket enclosing the thermocouples and made from heat transmitting material; said jacket having a head portion extending around the hot junctions of the second series and having a peripheral surface formed as a continuation of the exteriorsurface of the main body of the jacket.

References Cited in the file of this patent UNITED STATES PATENTS 2,349,306 Ray May 23, 1944 2,494,833 Ray Jan. 17, 1950 2,519,785 Okolicsanyi Aug. 22, 1950 2,526,112 Biggle Oct. 17, 1950 2,677,004 Biggie Apr. 27, 1954 2,677,712 Biggle May 4, 1954 acad -.17